Revetment



INI/ENTOR, L an don A?. Mason ATTORNEY l 9 4v l man l 4 m 9, a. M u N M o. ma V e v. .l .R m D ya d e L l .l F

`Fam. 8, 1935.

Patented Jan. 8, 1935 PATENT OFFICE nEvETMENT Landon R. Mason, Los Angeles, Calif., assigner to Union Gil Company of California, Los Angeles, Calif, a corporation of California Application December 19, i932, sensi No. aus s claims. (ci. 61-3'1) 'I'he present invention relates to revetments, earth dams, levees and like types of embankment protections. In particular, the invention relatesto embankment protections containing a bituminous mastic or concrete and to pre-cast rein, forced slabs of asphaltic mastic or concrete for lining the surfaces of river banks, ditches and the like. I

Among the typesof embankment protections' that have been developed for use along the banks of rivers, ditches, levees, etc., is one using a mattress composed of large pre-cast slabs of Portland cement concrete. 'I'hese slabs are used for all of the sub-aqueouswork and to some extent for the work lying. in the border' zone Just above the waters edge when it is at its lowest stage of flow. The

upper bank protection is paved with a mat or sheet of Portland cement concrete. Aside from the fact that this type of bank protection is very expensive, it requires constant maintenance due to the destructive action of water in nood times and dueto the impacts of oatinglogs, rolling stones and similar objects which are sufllcient in some instances to' completely destroy the bank protection of Portland cement concrete. Moreover, the irregularities in the surface of the banks over which the Portland cement concrete slabs are placed, caused either by poor grading or by thev washing away of the earth under the mattress of slabs or the monolithic mat, leaves the structure unsupported to such extent that a slight impactl will effect cracking and destruction.` Another disadvantage to the use of Portland cement con-,- crete is the contracting eifect of the concrete after expansion which results in cracking of the structure. Revetments constructed of Portland cement concrete thus require constant supervision, repair and maintenance. In some places, such as along the banks of the lower Mississippi River, large sums of money are spent each year and after each flood to maintain the revetment in repair from the damage caused by floods. f

One of the primary objects of my invention is to correct the aforementioned dimculties and disadvantages attending prior revetment construction and 'to present a revetment which cannot be easily cracked and destroyed.

Another object of this invention resides in a revetment which is self-healing when cracked and one which is sumciently flexible to follow the contours of the bank which it protects.A

Another object of this invention resides in a revetment constructed of an asphaltic mastic or concrete which is tough, dense, flexible and selfhealing. Another object resides in a method of constructing revetments employing asphaltic mastic or concrete.

Another object is in a pre-cast revetment slab of great strength which is lower` in cost, more simple in construction and of greater durability than any pre-cast revetment slab heretofore used. It is another object of this invention to present a pre-cast slab adapted for use in revetment construction made of asphaltic mastic or concrete.

Other ancillary objects of my invention will be suggested in the following description taken from the drawing and in the uses to which my invention is put.

- Referring to the drawing:

Fig. 1 is a perspective view of a pre-cast slab; Fig. 2 is a section of' lthe slab taken along line 2 2 of Fig. 1-;

Fig. 3 is an end view of a revetment construction shown partially in section;

Fig. 4 is an enlarged view of a mat on the slope shown in Fig. 3;

Fig. 5 is apartial plan view of the mattress of slabs shown in Fig. 3; v

Fig. 6 is an end viewof a modified revetment construction.

portion of the In its broadest aspects, my invention comprises a revetment containing asphalt, and, in particular, iilled asphalt. An important feature of my invention resides in a pre-cast 'slab containing filled asphalt which may be employed in revetment construction, said filled asphalt being preferably composed of asphalt and a ilnely comminutedilller such as diatomaceous earth combined in such proportions as to presenta mastic` of high tensile strength and resistance to 4impact and one which is self-healing when fractured.

More speciiically, my invention comprises a revetment containing nlled asphalt and comprising a mat or sheet containing asphaltic material which is laid on the slope of an embankment to be protected against water action and comprising also a mattress of a plurality of inter-locked precast slabs containing filled asphalt of high tensile strength and impact resistance attached to the embankment in hinged relation so as to follow the contours of' the surface over which it lays.

It is an important feature of my invention to present a revetment comprising iilled asphalt and crushed stone or aggregate laid in the shape of -a mat or sheet, said illled asphalt comprising a mixture of between 5 and 30% of a nller such as diatomaceous earth and/or rock dust or' other suitable filler and approximately 'l0 to 95% lof a D grade steam refined asphalt, said filled asphalt having a tensile strength of approximately A 300 lbs. per square inch and an impact resistance of upwards of approximately 2.5 ft. lbs. when mixed with Ottawa sand in amounts sufficient to exactly i111 the voids in the sand.

My invention also includes a method of constructing revetments comprising compacting a course of broken stone-,on an embankment to be protected and filling' the voids inthe course of broken stone with filled asphalt or asphaltic mastic, then laying a second course of broken stone over the rst course and filling the voids in the `second course with filled asphalt and preferably reinforcing the revetment with wire fencing or the llike laid intermediate the first andV second courses.

I have discovered that if banks to be protected are lined with a specially designed. bituminous mastic or concrete, the life of the revetment is lengthened considerably due to the great tensile strength, resistance to impact, 'permanent flexibility and self-healing properties of said bituminous mastic or concrete. I have also discovered that if the precast slabs of Portland cement concrete vheretofore employed for revetment construction are replaced with pre-cast slabs of asphaltic concrete or mastic, that va revetment is presented which is more iiexible than revetments sand and/or crushed rock comprising the aggregate shall be termed asphaltic concrete. I particularlydesire to employ filled asphalt rather than pure asphalt for admixture with aggregate to form the yasphaltic concrete because filled asphalts possess greater toughness, reasonable high ductilitiies,7 high melting points and substantially low penetrations and have 4very little tendency to become unstable even when mixed with mineral aggregate )n extremely high concentrations as I have i'ound necessary in asphaltic concretes for lling the voids in the aggregate.

45 the cementing agents for the crushed rock or ag- The uned :splints which 1 desire to `employ as gregate are described in my co-pending application, serial No. 647,850 sled Dec. 19, 1932. Briefly, thesev asphalte may be described as comprising a mixture of D" grade steam refinedasphalt and a filler such as diatomaeeous earth or rock dust or a combination of such nllers. A

D grade asphalt is a steam refined asphalt having a penetration of 40 to 90 at 77 F., a melting or softening point of 110 to 130 F. and a ductility of greater than 100at 77 Il'.

The optimum concentrations and character of fillers to be used in building the pre-cast slabs or for lining the bank with monolithic asphaltic concrete or mastic are also described in said copending application.. The filled asphalt suitable for usein making the slabs and for lining the bank should conform with the following speeications:

softening point 175 r. or over Penetration at 77 F.-- `15 to 45 Penetration at 115 F... 120 orl less Ductility at'l'l F 5 or over Tensile strength 300 lbs. per sq. in. or over Impact resistance 2.5 ft. lbs. or over For determining the softening point, penetration and ductility of the the following methods outlined by the Anm'ili wlety ofTesting Materialssballbeused:

softening or melting point, ball and ring method D-36-26 Penetration D-5-25 Ductility D-113-28T The tensile strength shall be determined by making one inch cubical briquets in molds commonly used for preparing tensile strength test briquets of Portland cement. The briquets shall be composed of standard to 30 mesh Ottawa sand mixed with the proper quantity of asphaltic mastictoexactlyiillthevoids'inthettawasand which` comprises 32%% by volume. Afterk the briquets have cooled they shall be placed for one hour or more in a water bath at 77 F. and shall then be pulled apart in a suitable testing machine for determining tensile strengths.. f

The' impact resistance shall be determined by making two inch cubical briquets in molds and the briquets shall be composed of standard 20 to mesh Ottawa sand mixed with the proper quantity of asphaltic mastic to exactly till thel Vvoids in the Qttawa sand which comprise 32%% by volume. After the briquets have cooled, they shallbeplacedforonehourormoreinawater bath at 77 and shall be tested by dropping a two inch steel ball weighing 1.175 lbs. upon the cube..

allowingtheballilrsttodropsixinchesandthen progressively increasing the height of fall one inch per blow until destruction of the cube results. 'Ihe impact resistance may then be calculated by multiplying the helsht of fall in feet at cube destruction by the weight of the steel ball in pounds, that is, 1.175.

- As asphaltic mastic having the above designated characteristics may be produced by hot mixing from 30 to 72% by weight of "D" lgrade steam refined asphalt and 28 to 70% by weight of nller or combinationof fillers, such as dlatomaceous earth and rock dust, as determined in my above asphalt and 28% by weight of diatomaceous earth will conform with the above specincations asto' softening point, penetration, ductility, tensile strength and impact resistance. Likewise,;a mixture of 57% asphalt, ail/2% diatomaceous earth and 215595 rock dust and also a mixture of equal parts of asphalt and tlller where the filler comprises equal parts of diatomaceous earth and rock dust will have suchv specifications as indicated above but it will be observed that the ductilities of mixtures containing rock dust are less than when using straight diatomaceous earth. A mixture of 30% asphalt fand 70% rock dust will also be within the specifications but the ductllity is considerably lower than when using diatomaceous earth alone or in admixture with the rock dust.

The preferred assleste used for admixture with nlled asphalt to'produce the asphaltic concrete comprises a mixture of hard, cleanfsharp,y graded sand having the crushed stone and clean followingspeciiications:

Per cent Passing a 200 mesh sieve 6 8 Passing a 80 mesh sieve 14-20 A Passing a 40 mesh sieve 26-34 Passing a 10 mesh sieve 36-44 Passing a 3 mesh sieve l 54-64 Passing a screen with S in. circular t openings c 7&-88

Passing a screen with in. circular 0Min In admixing filled asphalts with commercial -aggregates,acare should be taken to adjust the ssi-16o' mentioned co-pending application. For example, fm.

a iilled asphalt composed of 72% by weight ofI gregate which has also been heated to temperay percentage of filled asphalt to exactly fill the voids in the aggregate since the maximum tensile strength and resistance to impact is obtained4 when the voids are exactly iilled with the lled asphalt. The amount of filled asphalt employed will, of course, vary with the percent of voids in the aggregate and the latter may vary from 15 to 25%4 by volume in dense mixtures. Consequently, approximately 15 to 25% by volume of the nlled asphalt must be employed to exactly fill the voids of the remaining 75 to 85% by volume of the aggregate.

It is preferable to choose an aggregate having a maximum density, that is, having a minimum of voids. By carefully proportioning the amount of sand to crushed rock, it is possible to obtain an aggregate having a minimum of voids. I have found that an aggregate composed of crushed rock.

capable of passing a screen having 1% inch circular openings and graded sand in the proportion 50.0% to 49.5% by volume, respectively, has a smaller percentage of voids, i. e., approximately 20.5% by volume than anyother combination of these materials. Consequently, approximatelyI 20.5% by volume of asphalt will exactly lill the voids of this aggregate to produce an asphaltic concrete of maximum density.

The pre-cast slab of asphaltic concrete `or mastic shown in Figs. 1 and 2 are approximately tenfeet long, six feet wide and from two to four inches thick. The slab is preferably built in several courses 11 and 12 of asphaltic concrete or mastic and is provided with1 several rods 14 of steel, iron or other suitable metal which are placed diagonally in the center of the slab as shown. Each rod is preferably provided with rings 15 on each end protruding from the corners of the slab to pmit interlocking at the four corners with adjacent similar slabs by means of cables, rings, clips and like fastening devices. 'I'he slab is provided with suitable reinforcing 16 lextending centrally through the slab.

Pre-cast asphaltic concrete slabs 10 may be.

constructed according to the following method:

A rectangular steel form of the required dimensions for the slabs, such as to length, width and.

thickness and similar tofthe forms used in constructing slabs of Portland cement concrete is placed on a level surface of such material yas will prevent sticking of the 'slab to be constructed-'to the surface. If desired. the surface may be covered with Manila paper in order to prevent bonding of the slab to the surface. Steel or iron rods l `14 of about %inch in diameter provided at each end with rings 15 and somewhat longer than the diagonal length of the form are placed diagonally across the form in such manner as to permit the ends to protrude out of the corners of the form. The rods are placed about half way into the thickness of the form. One way of permitting the rods to be placed half way into the form is to slit the corners ot the form to the required depth so as to permit the rods to rest at the corners of the form.

Ir desired, the intersection 17 er the diagonally placed rods may be tied with wire. I.Asphaltic concrete composed of filled asphalt, graded sand and crushed rock at a temperature of 250 to 450F. is

then poured into the mold and is tamped to ex.

actly fill the mold.' After the asphaltic concrete has cooled and hardened sufficiently to permit its removal, the slab is removed from the mold. The asphaltic concrete is preferably prepared by first forming the lilled asphalt by mixing asphalt and filler at a temperature of 350 to 500 F. and then mixing the iilled asphalt while hot with the agtures approximating that of the asphalt. If desired, approximately 20% by volume of the filled asphalt composed of equal parts by weight of asphalt and filler where the filler comprises equal parts by weight of diatomaceous earth and rock dust may be mixed with approximately by volume of aggregate composed of crushed rock and sand.- Preferably, I desire to employ a filled asphalt composed of 28% by weight of diatomsceous earth and 72% asphalt because it is possible to use more asphalt when using diatomaceous earth to produce a lled asphalt of a given high.

tensile strength and ductility than when usingrock dust either alone or in admixture with diatoms- After placing the form oh a suitable surface, as y vstated previously, a course 11 of one totwo inches of `crushedstone of such size as to pass a screenl of V4 in. circular openings is placed in the form. The rods 14 are then placed in the form and nlled asphalt of theabove stated composition,` i. e.

asphalt, 25%. diatomaceous earth and 25% rock dust, is poured or sprayed into themold at 250 to 450 F. in amounts sumcient to iill the voids in the' crushed stone and to completely cover the surface of the crushed stone.y A second course 12 of one to two inches of'crushed stone is laid over the first course of crushed stone and filled asphalt and hot filled asphalt is again applied yas before. Immediately after the second application of lled asphalt, screenings 18, such as gravel, are broomed .over the. slab and the entire slab is consolidatedv by tamping or rolling. When the slab has cooled and hardened sumciently topermit removal. it is removed from the form and isi ready for use. `If desired, screenings 18 may' also be provided for the -lower face of the slab by placing them in the mold prior tothe building up of the slab.

-If desired, and the same is quite. preferable, reinforcing 16 is placed between the first and second courses 11 and 12 of crushed -rock and lled asphalt is preferably placed on the first' course of asphalt. The reinforcing may consist of any acceptable wire fencing or any other type of inter-v crushed rock and filled asphalt and should .be 1

thoroughly covered with lledasphalt so that: it

will be bonded to the courses between which it lays. The mesh of the, fabric used should be large enough to permit the interlocking of the courses .crushed stone prior to filling'the voids with lled betweenvtl'iel mesh. 'If a non-metallic mesh is used, the material lshould be lsaturated with asphalt or asphalt containing finely divided mineral filler., v

The above described pre-cast slabs are employed in revetment constructionl known as butt-slab revetments, that is, where the ends of each slab are 4 abutted against adjacent slabs and are held together by means of cables, rings or clips passed through the rings protrudingfrom the corners of the slab. In such cases, the metal rods carrying the loops to permit joinder of -adjacent butt-slab revetments are necessary. However, I do not wish to be limited to the exact mode of placing the rods in the slab since the rods may be placed in other istics of slabs constructed of my asphaltic conthe entire slab wasconsolidated with crete, I have made certain tests which show the desirability of using pre-cast slabs of asphaltic concrete for revetments rather than slabs of Portland cement concrete. I have made slabs of asphaltic concrete 27 inches wide, 36 inches long and 2 inches thick in a manner similar to that disclosed above for making slabs for use in revetments. However, the steel rods were omitted but the reinforcing was used. For example, a

f one inch course of small crushed stone was placed in the form and filled asphalt composed of '12% by weight of D grade asphalt and 28% by weight of diatomaceous earth at 450 F. was poured by means of a pouring pot over this course in amounts suiiicient tofill the voids in the crushed stone. Wire fencing for reinforcement was placed over this course and then a second one inch course of crushed stone was laid over the reinforcing and rst course.4 Hot filled asphalt was again applied to the crushed stone. Immediately after the second application of asphalt, screenings were broomed over the .slab and a hand tamp.

Portland cement concrete slabs of exactly the same size as the asphaltic concrete slabs and with the same type of reinforcing mesh wire were prepared. The concrete had a composition by weight of one part Portland cement to four parts of clean, sharp, graded sand which is used by the U'. S. Government to line the banks of certain rivers. A concrete of this composition is stronger than concrete containing one part Portland cement, two parts sand and four parts crushed stone.- These slabs were cured for seven days under water prior to testing.

After seven days of aging, a slab of Portland cement concrete and a slab of asphaltic concrete were subjected to impacts of a falling hammer weighing ten pounds dropped from a height of three feet. Each of the slabs to be tested were removed from its form and placed on a dry sand bearing three to four inches thick .and in such position that when the hammer was allowed to fall, it struck exactly in the center of the slab. The hammer was then struck upon the slab from a height of threefeet. On the secnd blow from three feet, the Portland cement concrete slab cracked through its entire length and was held toget'her merely by the reinforcing. It was completely destroyed a few blows thereafter. 'I'he reinforced asphaltic concrete slab was then tested in exactly the same manner after first thoroughly chilling it by cooling it with cold water in order to make the test as drastic as possible and to imitate practical conditions. One hundred blows from a height of three feet produced no fracture whatever and merely beat down 'a slight depression under the hammer due chiefly to the smashing of the screenings which formed the upper course of the slab.

To illustrate the flexibility of the asphaltic concrete slab, it was placed across a pile of sand so that the slab was supported only at its'center.

The results of this test showed that although the slab bent to follow the contour of the sand pile, it did not crack. 'To illustrate the self-healing characteristics, theslab was purposely cracked Vstated above and composed of 32%% by volume of filled asphalt comprising 28% 'by weight diatomaceous earth and 72% by weight asphalt and 675570 by volume Ottawa sand showed tensile strengths of approximately 400 lbs. persquare inch, whereas similar tests on one inch cubical briquets of one part Portland cement and three parts'Ottawa sand revealed tensile strengths of merely 210 lbs. per square inch.

It is thus apparent that pre-cast revetment slabs of filled asphaltic concrete are superior to those made of Portland cement concrete with regard to tensile strength, resistance to impact and flexibility. Furthermore, asphaltic concrete slabs are superior with respect to the self-healing property after fracture which, of course, is not apparent in the Portland cement concrete slabs.

An example of the method for constructing a reinforced asphaltic concrete revetment is as follows:

After the slope of the bank 19 (Fig. 3) is carefully graded to a 1 on 2 to 3 slope, a mat 20 of asphaltic material is placed on the bank. This mat is constructed by spreading a course 2i of broken stone 22 of l to 3 inches in thickness over the embankment or ,slope to the toe of the bank. The stone is then compacted and brought to a proper cross-section. In this construction, the

sand forming the smaller aggregate may be or it may be spot welded. 'I'hewire netting may f be anchored by means of pins 24 at both the upper and lower ends ofthe embankment in order to maintain the reinforcing stretched tightly. Hot asphalt, into which has been thoroughly mixed from 5 to 30% by weight of diatomaceous earth and/or other suitable llers, such as rock dust, is then applied over the broken stone and reinforcing until all 'of the voids are lled and the surface is completely coated. lAny suitable means, such as pumping, spraying or pouring, may be used for applying the illled asphalt to the course of broken stone and reinforcing wire. The amount of illled asphalt required will vary from one-half to three gallons per square yard depending upon the percentage of voids in the course. .The percentage of voids is dependent tire surface is compacted by tamping or rolling.

It will be observed by reference to Fig. 4 that the broken stone 22 employed for the base course may be larger than the broken stone 26 of the top course. For example, the base course may be prepared with broken stone capable of passing circular openings in diameter equal to the thickness of the base course, whereas the crushed stone used for the top course may be of such size as to pass a screen having circular openings of one inch in diameter. If desired, smaller size crushed stone, such as will pass a screen having circular openings of one-half inch diameter may be mixed with the base course of broken stone to fill the voids in the broken stone prior to the application of the filled asphalt. Likewise, sand and/ or gravel may be worked into the base course. Gravel and/or sand may also be mixed with the crushed stone of the top course prior to the spraying of the course with filled asphalt.

It is preferable to provide the toe of the slope with a thick wall 30 of about one foot thick of asphaltic concrete extending several feet into the ground. The purpose for this is to prevent water from washing the earth under the asphaltic mat particularly at the toe of the slope.

If desired, and where the slope of the bank to be protected permits, the bank may be lined with Aby hot mixing as stated above.

crete of the top course but in all cases the amount of filled asphalt used should be sufiicient to exactly iill the voids in the aggregate.

The surface 29 below the toe of slope is preferably lined with a mattress of pre-cast slabs 10 of asphaltic concrete made in the manner described above. Each slab is interlocked or fastened to adjacent slabs by means of cables, rings or clips 31 passed through the rings 15 provided on the slabs as shown in plan in Fig. 5. The slabs are preferably laid with their lengths parallel to the bank. 'I'he mattress composed of a plurality of slabs interlocked, as stated, is tied to the embankment in hinged relationship by means of cables or wire 32 passed through the rings 15 of the slabs adjacent the toe of the slope and the ring of anchors 33 which are-embedded in the asphaltic concrete at the toe of the slope. A mattress of this character is quite flexible and will follow the contour of the surface over which it is laid should the earth under the. slab structure be washed away.

If desired, instead of a butt-slab mattress as described above, a lap-slab mattress may be employed for lining the river bed below the toe of the slope. are laid in much the same manner as the laying of shingles on a roof and as shown in Fig. 6. An overlap 40 of approximately one foot is suilicient to retain the slabs in place. When the river bed is dry, it is desirable `to cement the overlapping section 40 to the lower slab by means of an asphaltic cement. This type of structure is also quite flexible and should earth thereunder be washed away, 4it also will follow the contour of the surface.

In such cases, the pre-cast slabs 10 While the above invention has been described tic ingredient or cementing agent since unfilled asphalt, air blown or emulsied asphalt may be used. Furthermore, other bituminous products having more or less cementing characteristics may be employed such as cracked and uncracked petroleum residues, cracked and uncracked coal tar residues, pitch, tar and the like.

The above disclosure is to be 'taken as merely illustrative of a preferred embodiment of my invention and is not to be considered limiting, since many variations thereof may be made within the scope of the following claims:

-I claim:

1. A revetment structure for protecting embankments comprising a mat of filled asphalt and aggregate on the slope of said embankment and a mattress disposed adjacent said mat andI extending beyond the toe of said slope, said mattress comprising a plurality of slabs of asphaltic concrete composed of filled asphalt and aggregate, the'slabs being disposed ln adjacent relationshipfto each other to give a structure capable of adapting itself to changing contours in the foundation on which it is laid.

2. A revetment vstructure for protecting embankments comprising a course of reinforced asphalt concrete composed of filled asphalt and aggregate on the slope of said embankment and a mattress disposed adjacent said course and extending beyond the toe o said slope, said mattress comprising a plurality of interlocked slabs of asphaltic concrete composed of filled asphalt and aggregate.'

3. The revetment structure as in claim 1 wherein the slabs are in lap-slab arrangement.

4. The revetment as in claim 1 wherein the mattress is flexibly secured to the embankment.

5. A revetment structure for protecting embankments comprising: a mat containing asphalt on the slope of said embankment and a mattress disposed adjacent said mat and extending beyond the toe of said slope, said mattress comprising a plurality of slabs of asphaltic concrete composed of filled asphalt and aggregate, the slabs being disposed in adjacent -relationship to each other to give a structure' capable of adapting itself to changing contours in the foundation 0n which it is laid.

LANDON R. MASON. 

